Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $62.72   5.560%   $66.2072   $66.21   $66.20   $66.20  
  Purchase #2 $62.88   8.290%   $68.0928   $68.09   $68.10   $68.10  
  Purchase #3 $51.55   11.694%   $57.5783   $57.58   $57.60   $57.60  
  Purchase #4 $212.44   4.315%   $221.6068   $221.61   $221.60   $221.60  
  Purchase #5 $208.99   11.193%   $232.3823   $232.38   $232.40   $232.40  
  Purchase #6 $237.65   8.231%   $257.211   $257.21   $257.20   $257.20  
  Purchase #7 $84.26   9.169%   $91.9858   $91.99   $92.00   $92.00  
  7 purchase totals = $920.49       $995.0642   $995.07   $995.10   $995.10